The present invention relates to a technology of adjusting a light quantity in an image display apparatus.
In recent years, it happens that a semiconductor light source, such as a light emitting diode (LED) or a laser diode (LD), is used as a light source of an image display apparatus such as a projector or a television receiver (refer to JP-A-2007-19476).
With these semiconductor light sources, it can happen that a correlative relationship between an applied voltage and a light quantity (a voltage/light quantity characteristic) changes due to a temporal deterioration or an ambient temperature change. Then, in this case, even when providing the semiconductor light source with the applied voltage based on the voltage/light quantity characteristic before the change, it becomes impossible to emit a desired light quantity. Therein, to date, a voltage/light quantity characteristic review has been carried out after shipping the image display apparatus. Specifically, the applied voltage has been changed, the light quantity measured at each voltage, and the voltage/light quantity characteristic corrected based on such measurement data.
However, the measurement of the light quantity for reviewing the voltage/light quantity characteristic has been carried out utilizing a period in which a screen is comparatively dark, such as a flyback period when displaying an image. This is in order, as far as possible, not to let a user see a change in the light quantity caused by a change in the applied voltage. However, as the flyback period is extremely short at, for example, approximately 1 mS at an XGA resolution, it not being possible to sufficiently carry out the measurement of the light quantity, it has only been possible to acquire an extremely small amount of measurement data. As such, it being extremely difficult to correct the voltage/light quantity characteristic after the change to a high degree of accuracy, it has been extremely difficult to display an image with a desired light quantity.
As the voltage/light quantity characteristic can change, not only in the case in which the semiconductor light source temporally deteriorates, but also in a case in which a usage environment (a temperature and the like) of the image display apparatus changes, the heretofore described problem can occur. Also, the heretofore described problem, not being limited to the case of using the semiconductor light source, can also occur in a case of using a lamp light source, such as a UHP (Ultra High Performance) lamp or a metal halide lamp. Also, the heretofore described problem can also occur in a configuration wherein the light quantity is adjusted by a supplied current instead of the applied voltage.